1415 75TH ST SW BASE FILE 2016-01-01 MF Import

0'Donnell, Dric,ham 6 Partners, N. W. E-154U May 19, 1981 Page 11 excaval:i��n With a large backtioe or dragline, or by some other si�,itab)e mettiod that Will completely remove ttie soft organic soils. If any of tl�ese soils are allowed to remain beneath the f111s, they will create a potentially unstable slope plane. Probing alorg the edge of the sw�mp indicates that the organic mater.ials extend to a deptli of up to about nine (9) feet in the area oE tlie pro��osed slope. Tlie excavation will extend below the groundwater level. Tliis will require deWatering of ttie excavation before structur.al fills are placed, or by placing rock to a point above ttie water level to provide a firm base for the placement oE structuial fill. Bither meChod will require close coordination between the contrar.tor and Carth Consultants, Inc. Ple suggest that a pce-construction meeting be held to evaluate the contraotors procedures for the placement of this and ott:er deep fills. The removal of the organic materials should be conducted in relatively short sections and in ,uch a manner as to provide an essentially hor{zontal sucface on which Co plare and key the structural fill toe of tl�e proposec] :lope. Tlie structural fill should be placed and compacled as rapidly as possible to a point above ttie surface of tlie existin9 swamp betore tlie excavation ot tl�e adjacent section is begun. Curllier, once the structural fill begins to extend up tlie existing site grade it will be necessary to bench the fill into tl�e existing slope. All structural fill sliould be placed on stable ground in eigl�t (0) to ten (10)-incli tliick loose lifts and compacted to a minimum of 95 percent relative compaction as determined by ASTM D-1557-70 (Plodtfied Proctor). Fills sliould be benctie�i as tliey are placed on slopes steeper than 4:1.(horizontal:vertical). The upper slte soils and existing tills contain an excessive amount oE fines wl�icli were wet at tlie time of our field explora- tion. TIiIs condition may make tliem difficult to work or com- pact in their present state. We do not recommend their use as structural fill during wet weather or when the in-place moisture content is more than two (2) percent above the optimum moisture c�ntent. The lower till sotls may be suitable for structural fills provided ttiey are worked duriix� dry weatlier. If any of the grading is to be conducted duriiig wet weather, we recommend that granular naterials witi� a maximum size ot tWu (2) inclies, containing less than 5 percent Cines, (material passing the No. 200 steve) be used for struclural f.ill. Uuring dry weather, ottier granular materials, including ttie site till soils, nay be used provided the;� can be properly compacted. • Imported Eill sam- ples st�ould be submitted to Eartl� Consultants, Inc. Eor evalua- tion prior to brinying them on the site. 7'he placement ot the structural till chould be moni Corr��l ancl Cest��d by Earl:h Consul- tanCs, Inc. Fi,iL• G��isullnnls, Inc.